Ion implantation techniques are commonly used as one of the processes in the manufacture of integrated circuits. Ion implanters are used to modify the electrical transport properties, i.e. conductivity, in predefined regions of semiconductor material by doping the predefined regions with impurity atoms. Ion implantation techniques generally involve generating a beam of a particular species of ions in an ion beam generator and directing the ion beam through a vacuum chamber into a target wafer supported on a substrate holder or platen assembly. The ion beam may be scanned across the wafer using either electrostatic and/or magnetic deflection of the ion beam. Other ion implantation systems involve either mechanically scanning the wafer relative to the ion beam or a combination of mechanical scanning of the wafer with electrostatic and/or magnetic deflection of the ion beam. Ion implanters for processing single wafers one after the other often use a hybrid scanning system in which the beam is scanned at a relatively fast rate in one direction across the wafer and the wafer is mechanically reciprocated to and fro in a transverse direction through the scanned beam.
In any of these systems, and in particular in high current and/or high energy ion implantation applications, during processing, the temperature at any point on the surface of the wafer may rise to a temperature that causes damage to the structures thereon. The temperature of the surface of the wafer at any point is a function of the ion beam power and the technique used for ion beam scanning and/or wafer scanning. Steps have been taken in the prior art to limit the maximum temperature at the surface of the substrate during processing. These attempts to limit wafer surface temperature include for example the use of wafer clamping systems to clamp wafers to a heat sinking surface and to enhance thermal conductance through the back surface of the wafer. In spite of these known wafer cooling systems, wafer processing speeds may still be limited by the need to avoid overheating the wafer or parts thereof.